Auxin does not alter the permeability of pea segments to tritium-labeled water

The possibility of an auxin effect on the permeability of pea (Pisum sativum L. cv. Alaska) segments to tritium-labeled water has been investigated by three separate laboratories, and the combined results are presented. We were unable to obtain any indication of a rapid effect of indoleacetic acid on the efflux of ^{3}\text{HHO}$ when pea segments previously "loaded" for 90 minutes with ^{3}\text{HHO}$ were transferred to unlabeled aqueous medium with indoleacetic acid. We were able to confirm that segments pretreated with ^{3}\text{HHO}$ plus indoleacetic acid for 60 to 90 minutes can show an enhanced ^{3}\text{HHO}$ release as compared with minus indoleacetic acid controls. However, this phenomenon appears to be due to an increased uptake of ^{3}\text{HHO}$ during the prolonged indoleacetic acid pretreatment, and therefore we conclude that auxin does not alter the permeability of pea segments to ^{3}\text{HHO}$ in either short term or long term tests. We confirm previous reports that the uptake of ^{3}\text{HHO}$ in pea segments proceeds largely through the cut surfaces, and that the cuticle is a potent barrier to ^{3}\text{HHO}$ flux.